According to online analytics company comScore , Americans watched 37 billion online videos on sites like YouTube, Yahoo and Facebook in April. In total, 181 million U.S. Internet users watched an average of 1,307 minutes of online videos last month. Those numbers are virtually unchanged from last month, but one area that has seen pretty spectacular growth over the last few month is online video advertising. According to comScore, U.S. Internet users watched almost 9.5 billion video ads last month. That's about 60 ads per viewer. What makes this number even more astonishing is that it was only in March of this year that the number of video ads topped 8 billion for the first time.

According to online analytics company comScore, Americans watched 37 billion online videos on sites like YouTube, Yahoo and Facebook in April. In total, 181 million U.S. Internet users watched an average of 1,307 minutes of online videos last month. Those numbers are virtually unchanged from last month, but one area that has seen pretty spectacular growth over the last few month is online video advertising. According to comScore, U.S. Internet users watched almost 9.5 billion video ads last month. That’s about 60 ads per viewer. What makes this number even more astonishing is that it was only in March of this year that the number of video ads topped 8 billion for the first time.

Overall, the number of overall video views and the number of minutes they watch online video has remained pretty stable. There are some small changes at the bottom of comScore’s top 10, with Amazon making a reappearance in seventh position with 30 million viewers and Turner Digital dropping out of the list. Google’s sites, of course, continue to dominate the charts with 158 billion viewers, followed by Yahoo (53 billion) and VEVO (49 billion).

Facebook, which is obviously having its day in the sun today, saw the number of video viewers on its site drop a bit from 45 million to 44 million, but in return, those viewers stuck around for 27 minutes now instead of just 21.3 minutes last month and also watched more videos per viewer than the month before (264 million).

As for video ads, Hulu leads the pack here with 1.6 billion ads streamed last month (though that’s down quite a bit from 1.75 billion the month before). Google is a close second with 1.3 billion ads delivered, followed by BrightRoll and video ad exchange Adap.tv.

With 48.6 ads per viewers, Hulu, also delivered a higher frequency of ads than any other service. YouTube, for example, only showed its average viewer 17.7 ads.